Hi teeteringhead; Love the phrase Alpha 5 Linear Navaid, but I don't think many people would understand it nowadays. A fine piece of IFR equipment. I have a lovely photo on the wall of a Sioux over the Menai Bridge. I did that navex in the Whirlwind, just prior to the sea and mountain phase. September '66. Was there ever such a date?: it seems as though from another world